Assessment of the Effects of Melatonin on Preoperative Anxiety and Postoperative Analgesia in Children Undergoing Surgery: a Prospective, Randomized Clinical Trial

Children between the age of 5 and 14 years scheduled for elective surgery will be prospectively enrolled between September 2012 and October 2013. A physician will perform the clinical examination for each child, and anamnestic data will be collected in the medical records. Exclusion criteria will be: patients who had taken benzodiazepines, opioid drugs, or other sedative in the previous month; those who had sedation previously, or those with a temperament disorder, patients undergoing emergency surgery. Patients will be randomly assigned to 2 groups based on whether they will receive 0.2 mg/kg (max 5 mg) oral melatonin premedication (group A) or 0.5 mg/kg (max 20 mg) oral midazolam premedication (group B) before induction anaesthesia with propofol. For elective surgery, premedication will be performed between 07:30 and 09:30 h. Approximately 40 min before the induction of general anaesthesia, patients will be transported in a quiet room in the operating suite where they will receive orally melatonin or midazolam. The melatonin will be prepared by a dedicated resident in a fixed volume of 5 ml adding water in a syringe without needle. To simulate the sweet taste of the formulation of melatonin used, midazolam will be expanded to the fixed volume with 5% dextrose. The content of the syringe, in both cases marked with a coded label, will be blindly administrated to patients by the attendant nurse, not involved in the study. The child's level of sedation will be assessed and recorded by a resident before the premedication and 40 min after the administration of melatonin or midazolam, using the University of Michigan Sedation Scale (UMSS). In the operating room, an initial bolus dose of 1 mg/kg of intravenous propofol will be administered to both groups, followed by similar bolus doses of propofol until the patient will be anesthetized. Children will be considered anesthetized when asleep and not arousable. Anaesthesia will be maintained with inhalated sevoflurane. The total dose of propofol administrated will be recorded by the anaesthetist blinded to premedication group assignment. To provide objective information on the physical condition of patients after anaesthesia, Aldrete scale will be calculated after 10 min from conclusion of anaesthesia. Preoperative anxiety and postoperative analgesia will be also assessed in both groups.